linux/lib/mpi/mpi-inline.h
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   1/* mpi-inline.h  -  Internal to the Multi Precision Integers
   2 *      Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
   3 *
   4 * This file is part of GnuPG.
   5 *
   6 * GnuPG is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License as published by
   8 * the Free Software Foundation; either version 2 of the License, or
   9 * (at your option) any later version.
  10 *
  11 * GnuPG is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, write to the Free Software
  18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19 *
  20 * Note: This code is heavily based on the GNU MP Library.
  21 *       Actually it's the same code with only minor changes in the
  22 *       way the data is stored; this is to support the abstraction
  23 *       of an optional secure memory allocation which may be used
  24 *       to avoid revealing of sensitive data due to paging etc.
  25 *       The GNU MP Library itself is published under the LGPL;
  26 *       however I decided to publish this code under the plain GPL.
  27 */
  28
  29#ifndef G10_MPI_INLINE_H
  30#define G10_MPI_INLINE_H
  31
  32#ifndef G10_MPI_INLINE_DECL
  33#define G10_MPI_INLINE_DECL  extern inline
  34#endif
  35
  36G10_MPI_INLINE_DECL mpi_limb_t
  37mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  38              mpi_size_t s1_size, mpi_limb_t s2_limb)
  39{
  40        mpi_limb_t x;
  41
  42        x = *s1_ptr++;
  43        s2_limb += x;
  44        *res_ptr++ = s2_limb;
  45        if (s2_limb < x) {      /* sum is less than the left operand: handle carry */
  46                while (--s1_size) {
  47                        x = *s1_ptr++ + 1;      /* add carry */
  48                        *res_ptr++ = x; /* and store */
  49                        if (x)  /* not 0 (no overflow): we can stop */
  50                                goto leave;
  51                }
  52                return 1;       /* return carry (size of s1 to small) */
  53        }
  54
  55leave:
  56        if (res_ptr != s1_ptr) {        /* not the same variable */
  57                mpi_size_t i;   /* copy the rest */
  58                for (i = 0; i < s1_size - 1; i++)
  59                        res_ptr[i] = s1_ptr[i];
  60        }
  61        return 0;               /* no carry */
  62}
  63
  64G10_MPI_INLINE_DECL mpi_limb_t
  65mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
  66            mpi_ptr_t s2_ptr, mpi_size_t s2_size)
  67{
  68        mpi_limb_t cy = 0;
  69
  70        if (s2_size)
  71                cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
  72
  73        if (s1_size - s2_size)
  74                cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
  75                                   s1_size - s2_size, cy);
  76        return cy;
  77}
  78
  79G10_MPI_INLINE_DECL mpi_limb_t
  80mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  81              mpi_size_t s1_size, mpi_limb_t s2_limb)
  82{
  83        mpi_limb_t x;
  84
  85        x = *s1_ptr++;
  86        s2_limb = x - s2_limb;
  87        *res_ptr++ = s2_limb;
  88        if (s2_limb > x) {
  89                while (--s1_size) {
  90                        x = *s1_ptr++;
  91                        *res_ptr++ = x - 1;
  92                        if (x)
  93                                goto leave;
  94                }
  95                return 1;
  96        }
  97
  98leave:
  99        if (res_ptr != s1_ptr) {
 100                mpi_size_t i;
 101                for (i = 0; i < s1_size - 1; i++)
 102                        res_ptr[i] = s1_ptr[i];
 103        }
 104        return 0;
 105}
 106
 107G10_MPI_INLINE_DECL mpi_limb_t
 108mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
 109            mpi_ptr_t s2_ptr, mpi_size_t s2_size)
 110{
 111        mpi_limb_t cy = 0;
 112
 113        if (s2_size)
 114                cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
 115
 116        if (s1_size - s2_size)
 117                cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
 118                                   s1_size - s2_size, cy);
 119        return cy;
 120}
 121
 122#endif /*G10_MPI_INLINE_H */
 123
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